In such a sound locating device the monitor portrays a body concretion which is to be destroyed, as far as possible in such a way as to provide sufficient information as to the position, size and condition of the concretion to allow the doctor carrying out the treatment to determine the nature and duration of the ultrasound shock waves which are to be applied in order to destroy the concretion.
When the target mark on the monitor is thereby located on the image of the concretion, the focus of the therapy transducer, and the concretion are coincident, so that the ultrasound shock waves can then be applied thereto.
Basically, it is advantageous for the sound head of the locating transducer, which is for example a B-scanner, to be brought as far as possible against the skin of the patient, in order to avoid reflection and multiple echoing of the ultrasound waves emitted by the sound head, thereby to obtain as clear an image of the concretion as possible. Where in any desired position of the locating transducer, the concretion, is, by reason of said multiple echoes or reflections, only portrayed indistinctly on the monitor, a locating transducer can be displaced in the direction of the focus of the therapy transducer, thereby to obtain a clearer image of the concretion. In this case, with the application of a simple B-scanner, the concretion is displaced from the focal range of the locating transducer, that is to say the image resolution decreases. In practice, a locating transducer having several focal ranges can be used. As a function of the distance of the sound head of the locating transducer, from the focus of the therapy transducer the focal range of the locating transducer can be selected by the operation of an actuating element, in which focal range the concretion is located at that time, in order to provide the best possible image resolution.
With the patient positioned on a treatment table, the locating transducer can be moved against the patient's skin (and hence in the direction of the focus of the therapy transducer). By manual operation of the actuating element, empirically the most suitable focal range can be selected in order to achieve as good an image resolution as possible. It is to be noted in this regard that concretions may be located at differing distances from the surface of the patient's skin. Thus, for example, a stone in the ureter lies relatively deep in the patient's body, whereas other stones lie nearer to the surface of the skin.